The present invention concerns a steering wheel for a motor vehicle having an optical finger navigation module, at least one further operating element, a steering wheel electronic system and a databus for data transmission between the optical finger navigation module and the steering wheel electronic system.
An optical finger navigation module (OFN) can be integrated as a sensor for the detection of finger movements in the left and/or right switch block of a motor vehicle steering wheel. A display menu can be controlled with the signals of this kind of switch block. Each, or at least one, switch block like this can additionally contain at least one further operating element, in particular a push button, for direct access to particular functions. For the most part, a switch block has several operating elements.
The sensor data of each optical finger navigation module and the activation states of each of the several operating elements would have to be transmitted by the respective switch block for further processing. In particular, the sensor data must be conveyed to the steering wheel electronic system and then to the HMI (Human Machine Interface) components, for example an instrument cluster or main unit (HU).
If the switch block 1 (MFS; multi-function switch) of a steering wheel of a motor vehicle has several push buttons 2, for example according to FIG. 1, then the signals from these push buttons 2 are to be transmitted via corresponding signal lines 3 to a steering wheel electronic system (LRE). As a rule, the LRE is equipped with a controller 5, which carries out the communication with the operating elements 2 via the signal lines 3. The switch or activation states of the operating elements 2 of the switch block 1 are therefore imported directly by the controller 5 in the steering wheel electronic system 4. For this, signal lines 3 depending on the number of operating elements 2 will be needed by each of the switch blocks 1 of a steering wheel to the steering wheel electronic system 4. The number of possible signal lines 3 is thereby limited by the size of the connector and the available building space inside the steering wheel.
As previously mentioned, a switch block of a steering wheel can also contain an optical finger navigation module 6 as a sensor for the detection of finger movements, as is sketched in FIG. 2. In addition to the structure in FIG. 1, then, an additional databus connection 7 is needed with the integration of the OFN 6 in the switch block 1 between the controller in the OFN 6 and the controller 5 in the steering wheel electronic system 4. There is usually not enough construction space for this additional databus line, or the additional databus lines and the corresponding plugs. In addition, the costs for this kind of steering wheel increase with the number of lines.
The object of the present invention therefore consists in reducing the construction space needed for the installation of an optical finger navigation module and at least one further operating element in a steering wheel.
According to the invention, then, a steering wheel for a motor vehicle is provided having                an optical finger navigation module,        at least one further operating element,        a steering wheel electronic system and        a databus for data transmission between the optical finger navigation module and the steering wheel electronic system,        
wherein                the at least one further operating element is directly connected to the optical finger navigation module via a signal line, and        the optical finger navigation module is designed in such a way as to receive a signal from the at least one further operating element and relay it on to the steering wheel electronic system via the databus.        
The at least one further operating element is therefore connected directly via a signal line to the optical finger navigation module, which as a rule is located near to the operating element for ergonomic reasons. In order to transmit the signal from the operating element to the steering wheel electronic system, the databus connection already in place between the optical finger navigation module and the steering wheel electronic system can then be used. Consequently, a separate data line from the operating element to the remotely-located steering wheel electronic system can be avoided.
The optical finger navigation module and the steering wheel electronic system each preferably have a controller, and the two controllers communicate with each other via the databus. Communication by means of the controller has the advantage that a physically simply-formed databus can be used.
The signal from the at least one further operating element can represent the state thereof. In particular, the signal can be a binary signal, which relays the pressed or not-pressed state of a button.
Furthermore, the OFN can be designed to process the signals from the at least one further operating element and to relay the processed signals to the steering wheel electronic system. In this way it is possible that a decentralized pre-processing of the signals from the operating element or elements is carried out in the OFN.
The steering wheel electronic system can furthermore be designed in such a way as to engage a power saving mode or active mode, and to change from the power saving mode to the active mode upon receiving a predetermined activation signal from the OFN. In this way it is possible for the whole steering wheel electronic system to remain in a power saving mode until it is actually used. As a rule, the actual use of the steering wheel electronic system is limited to a small fraction of the actual motor vehicle operation.
The activation signal for the steering wheel electronic system can be generated by activating the at least one further operating element. Therefore, using one and the same operating element not only is an instrument cluster operated, for example, but also with it an activation signal (e.g. a wake-up-signal) for the steering wheel electronic system is generated.
Corresponding to a further embodiment, the processing of the signals from the at least one further operating element can include the debouncing thereof. In this way, activation of the operating element can be reliably identified in a short period of time.
Moreover, the OFN and the at least one further operating element can be integrated in a single housing. This kind of housing represents, for example, the housing of a switch block, which can then be mounted as a whole unit in a steering wheel at low cost.
Overall, it is advantageous if a motor vehicle is equipped with the steering wheel described above and hence can profit from the present invention.
The present invention is described in greater detail by means of the attached drawings.